Long chain saturated aliphatic amino acids, lactams, and dibasic acids are important monomers for long chain nylons and engineering plastics. Nylons are a class of polymers that contain amide bond on their backbone of chains. Nylons are one of the most widely used, most numerous in types, and most consumed class of engineering plastics.
Because of their unusual molecular structure, long chain nylons possess extraordinary physical properties, i.e., higher mechanical strength than metal, low hygroscopicity, excellent resistance to oil, low temperature, abrasion, and chemical corrosion, and most importantly, easy to fabricate. Long chain nylons are made into many kinds of plastics products, spun to fibers, and stretched to thin films. Long chain nylons are also used in paints and hot melt adhesives. Hence, long chain nylons find wide applications in automobile, electrical, electronic, telecommunications, petrochemical, and aerospace industries.
Long chain amino acids and lactams are used industrially as monomers to produce nylon-9, nylon-11, and nylon-12.
Long chain dibasic acids are condensed with diamines industrially as starting materials to produce nylon-610, nylon-612, nylon-510, nylon-512, nylon-1010, and nylon-1212.
Among the current production technologies, the nylon-9 monomer, 9-aminononanoic acid is produced from oleic acid or oleonitrile by a series of chemical reactions (details are described in J. Am. Oil Chemist's Soc., 1975, Vol. 52, No. 11, pp 473-477).
For the nylon-11 monomer, 11-aminoundecanoic acid, is produced from castor oil through ester exchange with methanol, pyrolysis at high-temperature, free radical addition of anhydrous hydrogen bromide, and finally ammonolysis (detailed process is described by A. Chauvel & G. Lefebvfre, Petrochemical Processes 2: Major Oxygenated, Chlorinated and Nitrated Fatty acids, pp 274-278). The overall yield is not more than 55%.
The monomer of nylon-12, laurolactam, is produced from 1,3-butadiene through a series of reactions, i.e., trimerization to cyclododecatriene, hydrogenation to cyclododecane, oxidation to cyclododecanol or cyclododecanone, oximation, and Beckmann rearrangement (detailed process is described by A. Chauvel & G. Lefebvfre, Petrochemical Processes 2: Major Oxygenated, Chlorinated and Nitrated Fatty acids, pp 279-286).
In the industrial production of long chain dibasic acids, azelaic acid is produced from oleic acid by oxidation, while sebacic acid is produced by alkaline scission of castor oil or fatty acids at high temperature (200° C. to 250° C.), followed by purification and refining.
For the important dodecanedioic acid, there are two industrial processes of quite different nature. One is the chemical synthesis from 1,3-butadiene through catalyzed trimerization to cyclododecatriene, hydrogenation to cyclododecane, oxidation to cyclododecanol or cyclododecanone, and finally, oxidation by nitric acid. The other process is more preferable, i.e., biochemical oxidation of terminal methyl groups of high purity dodecane or lauric acid by fermentation.
In the production of these monomers by chemical synthesis, there exist problems for the current industrial processes, e.g., low overall yield (35% for 9-aminononanoic acid, 55% for 11-aminoundecanoic acid, 80% for sebacic acid), reaction conditions that are inherently dangerous and difficult to control. For example, the production of 9-aminononanoic acid requires the use of ozone, and the production of 11-aminoundecanoic acid requires a pyrolysis reaction at high temperature. Moreover, the production of laurolactam and dodecanedioic acid makes use of trimerization of 1,3-butadiene under inert reaction conditions with a flammable catalyst, while the production of sebacic acid requires a very corrosive alkaline scission of castor oil.
Although the reaction conditions are mild, fermentative oxidation of long chain alkanes or lauric acid via fermentation to produce dodecanedioic acid or other long chain dibasic acids, yields a crude product that contains a large amount of biomaterials and degraded short chain dibasic acids. To obtain a product suitable for the production of nylons, crude product must be subjected to complicated purification and refinement. Many methods to refine and purify the crude products are described in the literature. Detailed processes are disclosed in U.S. Pat. No. 6,218,574; U.S. Pat. No. 8,729,298; CN 104591998A; CN 102476990A; CN 102329224A; CN 103497100A; CN 102795989A; CN 104447274A; CN 104447280A; CN 104496793A; CN 104529741A; CN 104529747A.
WO 2017088218 by the present inventor discloses a novel process for the co-production of long chain amino acid and dibasic acid. According to the disclosed process, keto fatty acid ester or amide is reacted with hydroxylamine to form an oxime fatty acid derivative, which is subjected to the Beckmann rearrangement to form a mixture of two amide fatty acid derivatives. When the mixed amide derivatives are hydrolyzed, a mixture of long chain amino acid and dibasic acid is obtained and separated in high dilution.
The process according to WO 2017088218 starts from an inconvenient starting material, i.e., keto fatty acid ester or amide, which is not commercially available. Moreover, during the preparation of oxime, the ester is not stable and is hydrolyzed to produce a significant amount of an alkali salt of oxime fatty acid, which is soapy and renders processing difficult. Furthermore, this impurity interferes with the Beckman rearrangement and inactivates the catalyst.
During the hydrolysis of the mixed amide fatty acid derivatives, prepared according to WO 2017088218, to long chain amino acid and dibasic acid, a lower alcohol, i.e., methanol or ethanol, is released from the hydrolysis of ester group. This lower alcohol complicates the separation of alkylamine, particularly for hexylamine, which forms with an azeotrope with water The formation and separation of this azeotrope are greatly influenced by methanol or ethanol.
In addition, there is a need for the separation of short chain alkylamine and alkanoic acid, produced along with long chain amino acid and dibasic acid, for the process to be economically successful and environmentally safe.
It is an object of the present invention to overcome the disadvantages by disclosing a process for producing long chain amino acid and dibasic acid from hydroxy fatty acid, in particular, 12-hydroxystearic acid, which is a commercially available, stable starting material.